There were originally a total of nine patients, 11 from the bus and one from another vehicle.

Louisville Metro Police said the cause of the crash was a mechanical failure.

The driver of the truck who witnessed the crash said it looked like the bus' front left tire blew out.

"It swerved to the left really hard and hit the barrier," said trucker Lynn Wehling, who was just a few cars behind the bus when he witnessed the crash.

He was traveling westbound on I-64 near mile marker 23 when white smoke appeared and the bus swerved from the far right lane into the left median.

Wehling said the teens on board were fairly calm when he went to help.

"I wasn't thinking of anything else, but making sure everybody was OK. I helped try to get the kids that weren't hurt out of the bus and tried to get the other ones that were hurt calmed down," said Wehling.

A Jefferson County Public Schools spokesman said 73 students from Waggener High School were on two separate buses operated by Commonwealth Bus Services.

The 42 10th- and 11th-graders on the bus that crashed were taken to different hospitals, some as a precaution and others with serious injuries.

"There was blood and there was glass all over the place. There was a few of the windows and such that were blown out and stuff from the kids hitting their heads and what not on the windows," said Wehling.

The school district said they were returning from Eastern Kentucky University as part of a program that allows students to tour different colleges in the state.

LMPD spokeswoman Alicia Smiley said the bus crash resulted in another accident, adding to traffic delays on both sides of the highway.

"I'm not sure if they were rubbernecking or what the case was, perhaps just not paying attention, but apparently they also had a single vehicle accident," said Smiley.

All lanes of eastbound I-64 were re-opened around 5 p.m.

Westbound traffic was delayed until the bus was towed away around 7 p.m.